Fish Waste Composting In Pacific Northwest

North Mason Fiber in Washington State has mastered the art of composting large volumes of fish in aerated static piles.

Dan Emerson

BioCycle September 2013, Vol. 54, No. 9, p. 23

For over 10 years, North Mason Fiber in Belfair, Washington has been turning wood, green waste and other organic material into 18 different products, including compost, bark, mulch and hogged fuel. Bob Dressel started the company in 1989 to recycle wood waste from timber companies in the region into products for the paper industry. He began composting in 2003, and in 2006, ventured into unknown territory when he began accepting fish waste from food processors in the Pacific Northwest and turning it into high-quality compost, selling it under the brand name Oly Mountain Fish Compost.

When Dressel first became interested in making fish compost, one of the motivating factors was the environmental damage — specifically stagnation and oxygen depletion in some bays and harbors in the Puget Sound Basin — being done by the centuries-old practice of “fish dumping,” by fishermen and seafood processors. He estimates that the Oly Mountain operation diverts as much as 55 tons/week of fish waste from landfills. Dressel also knew that the high nitrogen content of fish would translate into high-quality, high-value compost. The fish-based compost has a higher nitrogen content than the company’s green waste compost (around 2% N vs. 1% N respectively), according to Dressel. “It releases that nitrogen slowly, over time — two traits that have made the fish compost a popular product,” he says. “Because of the slow release, you can plant directly into it, with no negative consequences.”

Panoramic view of North Mason Fiber’s fish composting process, including the grinding of wood and green waste, and making a receiving bed for the fish residuals.

Dressel, his partner, son Robb, and one employee operate the 30-acre facility in the North Mason Commercial and Industrial Park, processing as much as 80,000 tons/year of organics from waste haulers, a food processing company and U.S. Navy installations. At least a dozen seafood processors in the Pacific Northwest supply the fish waste, bringing in 1,200 to 1,750 tons/year in total, according to Tamara Thomas, owner of Terre-Source, a Mount Vernon, Washington-based environmental consulting firm that has been working with Dressel since he began the permit process for composting 11 years ago. Types of fish waste processed include salmon, hake, tuna, bottom fish, shark and sometimes ahi. Most is whole fish from offshore and onshore fisheries and hatcheries, and pet food companies. Dressel has to pay suppliers for the fish waste, and competes with other markets, particularly pet food and agricultural fertilizer manufacturers. “The price has gone up 70 percent recently, just because of the value of fish in the ag market, even though fish (waste) used to be the bastard child,” he explains. “But I don’t think the price increase is going to hamper us, because the product sells itself and people are willing to pay a little more for good quality, certified-organic fish product.”

Much of the fish arrives whole, coming from offshore and onshore fisheries and hatcheries. A key to composting fish waste is use of a bulking mixture that soaks up the moisture.

The facility has more than 28 acres of paved area with a fully contained storm water system for turning organic wastes into compost. It uses a Peterson Pacific 6700 horizontal grinder for the wood and green waste. One of the keys to the process is use of a bulking mixture made up of a mix of wood and green waste that soaks up the moisture from the fish waste. Although fish compost takes longer to produce, when the fish waste is originally received, it “kicks off really fast and you have to be on top of it,” says Thomas. “It’s not something you can bring in and let sit for a day without doing anything.”

The material is composted in positively aerated static piles, typically about 20-feet wide and 75- to 90-feet long. The piles are covered with a biofilter up to 3-feet thick, made of coarse woody debris and finished compost. The material remains under forced aeration for at least 28 days, and sometimes longer, “depending on how things are flowing,” Thomas explains. “The biofilter is a great odor control mechanism, and also shields the piles from the weather.” After being taken off aeration, the compost is cured for about two years.

Wood and green waste is ground using a horizontal Peterson grinder. In addition to the fish waste compost, North Mason Fiber sells a green waste-based compost. Both product lines are certified organic.

Dressel says it took a while to determine the best way to turn fish matter into finished compost, while preventing and minimizing the odors normally associated with decaying fish. “We were going out on a limb when we started doing this,” he recalls. “But fish has been used as a soil amendment for thousands of years in many cultures; it’s nothing new.” There was a lot of trial-and-error involved in developing an efficient, effective process. “When we started, we made the worst compost in the world for the first six months,” he adds. “It was sticky and oily. Because the fish has such a high nutrient level, we found out that the longer we cured and aged the compost, the better the product was.”

Finished compost is screened using a McCloskey trommel. North Mason Fiber is in a unique position as a fish-based compost supplier, Dressel notes. “We’re the only people in the state of Washington permitted to produce bag and bulk fish compost; it’s given us a huge niche market.” The company uses a Rotochopper Go-Bagger to bag the compost. The products (the company also makes a yard trimmings-based compost) are certified organic by the Washington State Department of Agriculture, and are sold under the Oly Mountain label in both bulk and 1 cu. ft. bags wholesale to garden-store retailers and landscapers in the region. The fish compost retails for about $6 to $9/bag.

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